Discard subject UTF8

[Emanuel]

Hello,

due to email accounts compromised by viruses, I have created filters for 
the subject of these malicious emails

/^Subject: Your Amazon\.co\.uk order \#[0-9]*$/    DISCARD

Now, I see that these malicious emails keep coming out but they are not 
discarded because the subject is encoded in utf8.

=?UTF-8?B?WW91ciBBbWF6b24uY28udWsgb3JkZXIgIzM2Njg1MDk2Nw==?=

How can I discard these emails if they are encoded? yes or if I need to 
create a regular expression for the ID in to the subject.

Regards,

--